ES2359660T3 - NEW ELECTRODES. - Google Patents

Abstract

The present disclosure provides electrodes that possess components capable of indicating to an end-user when the electrode is in need of replacement.

Description

CROSS REFERENCE WITH RELATED APPLICATIONS

This application claims the benefit and priority of Provisional Patent Application No. 60 / 984,869, filed on November 2, 2007, whose full description is incorporated herein by reference.

TECHNICAL FIELD 5

The present description refers to hydrogels suitable for use as conductive compositions, the methods for making these compositions and the use of these compositions with medical electrodes.

BACKGROUND OF RELATED TECHNIQUE

Hydrogels constitute a wide class of materials that can be completely soluble in water or can swell considerably in water but are not completely soluble in it. They have been used in 10 different biomedical applications and can be applied in bulk in mold meshes that vary from clear to opaque, and from a relatively thick to a relatively soft consistency. Sometimes bulk mold meshes are reinforced by reinforcement elements that can be woven or non-woven fabrics in order to increase the composite strength and / or dimensional stability. Hydrogels have also been used as coatings for various biomedical applications. fifteen

Medical electrodes are used to transmit signals or electrical currents between a patient's body and external medical equipment. These electrodes may include a conductive composition adhered to, or otherwise in contact with, the patient's skin, and a conductor that is electrically connected to the conductive composition and the external medical equipment.

Hydrogels for use as conductive compositions with medical electrodes remain desirable. twenty

Published patent application US 2005/0277991 sets forth the preamble of claim 1.

SUMMARY

The present description provides electrodes that have components capable of indicating to an end user when the electrode needs to be replaced. In embodiments, an electrode of the present disclosure may include a substrate and a conductive composition on at least a portion of a surface of the substrate, including the conductive composition 25 at least one hydrogel and at least one pH indicator component that changes its color or opacity due to a change in pH, which provides an indication to replace the electrode.

In other embodiments an electrode of the present disclosure may include a substrate and a conductive composition on at least a part of a surface of the substrate, including the conductive composition at least one hydrogel and at least one pH indicator component that changes its color or opacity. being exposed to a specified pH, in some embodiments from about 2 to about 4, in other embodiments from about 8 to about 10, which provides an indication to replace the electrode.

The methods for producing electrodes and their components are also provided, as are the methods for their use.

BRIEF DESCRIPTION OF THE DRAWINGS 35

Figure 1 is a top plan view of a medical electrode that includes the conductive composition of the present description.

Figure 2 is a view of a straight section of the medical electrode of Figure 1.

Figure 3 is a view of a straight section of a medical spring electrode.

Figure 4 is a view of a straight section of an alternative medical electrode to that of the present description. 40

DETAILED DESCRIPTION

Any adhesive application, including those involving fabrics, is within the scope of the hydrogel compositions of the present disclosure. In embodiments, hydrogels can be used as adhesive and / or conductive compositions for medical electrodes. The hydrogels of the present disclosure may include components that provide an indication to an end user that the hydrogel is reaching the end of its useful life and that therefore the electrode should be replaced.

As used herein, the term "hydrogel" may refer to a wide variety of polymer based compositions. These materials can be synthesized, for example, from monomers or from monomers mixed with

polymers or solutions of water crosslinked polymers. They can be obtained by chemical modification of existing polymers or by the addition of water to existing dry polymers.

A biocompatible hydrogel can be used in accordance with the present description. Generally speaking, a hydrogel according to the present description may include a coherent three-dimensional aqueous polymer system capable of immersing water without liquefying. In embodiments, water insolubility can be provided by crosslinking the hydrogel polymer. In embodiments, the hydrogels or gels of the present disclosure that contain water may include water and various chemicals that include gelatins; polysaccharides; crosslinked acrylamide polymers; hydroxyethyl methacrylate polymers; crosslinked polyhydroxyethyl acrylate; cross-linked 2-acrylamide-2-methylpropane sulfonic acid polymers or a salt thereof such as sodium or potassium type; polyvinylpyrrolidone; polyacrylic acid; copolymers of the aforementioned monomers, copolymers of the aforementioned monomers with other polymers such as polystyrene or other polymers that do not form hydrogels, one or more salts thereof, and combinations thereof.

For example, hydrogels can be formed by crosslinking homopolymers of an acrylamide derivative such as 2-acrylamide-2-methylpropane sulfonic acid or one of its salts. Copolymers of them can also be formed in the same way with acrylamide. So do crosslinked homopolymers of acrylic acid and methacrylic acid, their salts and copolymers also do, as do other crosslinked acrylic homopolymers and copolymers.

The hydrogels of the present description obtain their adhesive properties in part by their ability to absorb water. When a relatively dry hydrogel mass makes contact with moisture, such as moisture in the fabric, especially the internal tissue or any other wet surface develops an aggressive adhesive nature. When the hydrogel polymer is crosslinked to a suitable degree, the bulk hydrogel is hard enough, even when it has been swollen with additional liquid, to provide an adhesive cable support for cardiac electrostimulation thereby creating an expanded cable connection with the tissue.

Excessive crosslinking decreases the viscosity of the hydrogel. Crosslinking too low decreases its cohesion power. Thus, in the embodiments, a crosslinking agent can be used to form the polymer as a hydrogel of the present disclosure.

In use, a hydrogel of the present disclosure may contain the polymer or copolymer and any other additives, which include the components used to form the copolymer, in an amount from about 97% by weight of the hydrogel, the remainder being water and / or a moisturizer

In some embodiments, a hydrogel suitable for use as a conductive composition may include a copolymer. Non-limiting examples of suitable copolymers may include a first monomer such as a mixture of acrylic acid and a salt thereof, and a second monomer, such as one or more monomers selected from CH2 = CHC (O) XR, wherein X is O or NH and R is an unsubstituted or substituted alkyl group of 1 to 5 carbon atoms. The hydrogel can also include water, an electrolyte or a mixture of electrolytes; a polymerization initiator; a neutralizer such as sodium hydroxide; optionally a crosslinking agent; and optionally a thickener. 35

In embodiments, a first monomer that can be used to form a copolymer for use in a hydrogel includes acrylic acid, a salt thereof, or a mixture thereof. The copolymer thus produced by polymerization includes acid acrylate halves (CO2H and / or -CO2M, wherein M is a cation such as a sodium ion, a potassium ion, a lithium ion, an ammonium ion or a substituted ammonium ion , etc.) directly attached to the backbone of the polymer.

In the embodiments, a copolymer used in a hydrogel of the present disclosure may include a second monomer that may be one or more monomers selected from CH2 = CHC (O) XR, wherein X is O or NH and R is a unsubstituted or substituted alkyl group of 1 to 5 carbon atoms. The polymer produced by this polymerization includes groups of the structure -C (O) XR directly attached to the backbone of the polymer.

Unsubstituted alkyl groups are methyl, ethyl, n-propyl, n-butyl, and n-pentyl. Appropriate substitutes that may be present in a substituted alkyl group are halogens (such as F, Cl, or Br) cyano, carboxylic acid and salts thereof (i.e., -CO2H or -CO2M, where M is a cation) , phosphates and salts thereof. An example of such a substituted alkyl group is (acrylic acid-3-sulfopropyl ester), the potassium salt. Suitable second monomers include 2-acrylamide-2-methylpropane sulfonic acid (CH2 = CH-CONCH (CH3) 2-CH2-SO3H) and / or a salt thereof. Suitable salts include sodium, lithium, potassium, ammonium and substituted ammonium salts, and mixtures thereof.

In the embodiments, the second monomer used in a copolymer component of a hydrogel of the present description is the sodium salt of 2-acrylamide-2-methylpropane sulfonic acid (NaAMPS) (CH2 = CH-CONCH (CH3) 2CH2-SO3 -M +). Thus, in some embodiments the first monomer used in a copolymer component of a hydrogel of the present disclosure may include a mixture of acrylic acid and sodium acrylate, and the second monomer may include 2-acrylamide-2- sodium sulfonate methylpropane

The first monomer (acrylic acid and / or salt or salt thereof, calculated as acrylic acid) may be present in an amount from 8% by weight to about 85% by weight of the copolymer in the hydrogel, In embodiments, from about 10% by weight to about 80% by weight of the total amount of

copolymer in the hydrogel. The second monomer, in NaAMPS embodiments, may be present in an amount of from about 15% to about 92% of copolymer in the hydrogel. In embodiments from about 20% by weight to about 90% by weight of copolymer. in the hydrogel.

Optionally, an effective amount of a crosslinking agent or mixture of crosslinking agents can be used to form the hydrogel copolymer component of the present disclosure. An effective amount of crosslinking agent is an amount that produces a conductive composition with physical properties, such as consistency and adhesion, and desired electrical properties. Although the amount required will depend, for example, on the molecular weight of the crosslinking agent, the number of ethylenically unsaturated free radical polymerizable groups in the crosslinking agent, the amount of free radical polymerizable monomers present in the monomer mixture, when the Crosslinking agent is present, the amount of crosslinking agent will be present in an amount from about 0.01% by weight to 1% by weight of copolymer used in the hydrogel. In embodiments, from about 0.02% by weight to 0.08% by weight of the copolymer used in the hydrogel.

Appropriate crosslinking agents include free radical polymerizable monomers that possess more than one polymerizable group of ethylenically unsaturated free radicals. Numerous polymerizable crosslinking agents by initiated free radical polymerization are within the scope of those skilled in the art. Crosslinking agents include, for example, bis-acrylamides and methacrylamides, such as N, N'-methylene bis-acrylamide; esters of acrylate and methacrylate polyols, such as ethylene glycol diacrylate and methacrylate, diethylglycol diacrylate and methacrylate, trimethylpropane triacrylate and trimethylpropane triacrylate and trimethyl acrylate, triacrylate, triacrylate and triacrylates of 20 polyethylene glycol, such as polyethylene glycol diacrylates and dimethacrylates having a molecular weight from about 200 to about 600. In embodiments, a suitable crosslinking agent may include N, N'-methylene bis-acrylamide [(CH2 = CHCONH) 2CH2].

In embodiments, a polymerization initiator with the first monomer and the second monomer can be used to form a copolymer for use in a hydrogel of the present disclosure. An effective amount of a polymerization initiator can be combined with the monomers to form such a polymer. As used herein, an effective amount is an amount that produces efficient polymerization of the monomers under polymerization conditions to produce a hydrogel suitable for use as a conductive composition. Numerous free radical polymerization initiators are within the scope of those skilled in the art. The polymerization initiator can be a single compound or a mixture of compounds. For example, the thermal and / or photoelectric free radical polymerization initiators can be used.

Thermal free radical polymerization initiators may include nitrogen compounds, such as 2,2-azobisisobutyronitrile (AIBN). Appropriate thermal free radical polymerization initiators are described in "Photoinitiators for Free-Radical-Initiated Photoimaging Systems" by B.M. Monroe and G.C. Weed, Chem. Rev., 93, 435-448 (1993) and in "Free Radical Polimerization" by K.K. Dietiker, in Chemistry and Technology of UV and EB Formulation 35 for Coatings, Inks and Paints, P.K.T. Oldring ed., SITA Technology Ltd., London, 1991, vol. 3, pp 59-525. Suitable polymerization initiators of photoelectric free radicals include, for example, 1-hydroxycyclohexylphenyl ketone (HCPK, IRGACURE® 184); 2-hydroxy-2-methyl-1-phenylpropane-1-one (DAROCUR® 1173); 2 hydroxy-1- [4- (2-hydroxyethoxy) phenyl] -2-methyl-1-propane-1-one (IRGACURE® 2959), 2,2-dimethoxy-2-phenylacetophenone (benzyl dimethyl ketal, BDK, IRGACURE® 651), benzophenone, a mixture of 50 %% by weight of benzophenone and 50% by weight of 1-40 hydroxycyclohexylphenyl ketone (IRGACURE®500), and combinations thereof.

The polymerization initiator may be present in a copolymer used in a hydrogel in an amount less than about 1% by weight of the copolymer, In embodiments less than about 0.7% by weight of the copolymer, in other embodiments less than about 0.4% by weight of the copolymer.

The hydrogel of the present description may also include an electrolyte or a mixture of electrolytes. The electrolyte 45 may be a salt, such as lithium chloride, sodium chloride, potassium chloride, magnesium acetate, ammonium acetate, or a mixture thereof. In embodiments, a suitable electrolyte may include potassium chloride. The hydrogel can have the electrolyte in an amount from about 0.5% by weight to about 10% by weight of the hydrogel, in embodiments from about 1% by weight to about 8% by weight of the hydrogel. fifty

The hydrogel used as a conductive composition may also include a neutralizer. Bases such as hydroxides, amines, Lewis bases, and mixtures thereof can be used as neutralizers. Non-limiting examples of neutralizers include ammonium hydroxide, sodium hydroxide, potassium hydroxide, lithium hydroxide, combinations thereof, and the like. If acrylic acid and / or the second monomer, such as 2-acrylamide-2-methyl-propane sulfonic acid, are included as monomers in the formation of a copolymer for use in the hydrogel 55 it may be convenient to add a neutralizer for neutralize some of the acid, so that the pH of the mixture is between about 3 and about 6.5.

When used, a neutralizer may be present in an amount from about 2% by weight to 8% by weight of the hydrogel.

In addition to a free radical initiator, small amounts of free radical polymerization inhibitors with one or more of the monomers, and / or the crosslinking agent, and / or may be added to the mixture to prevent premature polymerization. of the reaction mixture. Free radical polymerization inhibitors include, for example, hydroquinone, 4-methoxyphenol, di-t-butyl-p-cresol, pyrogallol, t-butyl catechol, benzoquinone, 4,4'-thio -bis- (3-methyl-6-t-butylphenol), and 2,2'-methylene-bis- (4-methyl-6-5 butylphenol). When present, the amount of the polymerization inhibitor may be between about 0.01% by weight and about 5% by weight of the hydrogel.

In some embodiments, a thickener can be added to the hydrogel. Appropriate thickeners include rheological modifiers that allow the hydrogel viscosity to be adapted to allow its use as a conductive composition with a medical electrode. Non-limiting examples of such thickeners are silicon, gums including xanthan gum, polymers that include polyvinylpyrrolidone (PVP), polyacrylamides, polyacrylic acid (which include those sold under the name CARBOPOL®), their salts, the combinations of them, and the like. When used, a thickener may be present in a hydrogel of the present disclosure in an amount from about 0.1% by weight to about 8% by weight of the hydrogel, In embodiments from about 0.5% by weight up to about 5% by weight of the hydrogel. fifteen

Other conventional components of the conductive compositions may be present in the hydrogel. For example, humectants and medicinal agents, including antimicrobials, antiseptics, analgesics, disinfectants, and the like, can be added to the hydrogel.

Water is present in the mixture. The amount of water includes any water present in any of the components as well as any water added with the components that are in aqueous solution, such as the monomers, the crosslinking agent, the neutralizer, etc. In embodiments, humectants may be added to the aqueous phase of a hydrogel used as a conductive component in an electrode of the present disclosure. Among the humectants that can be used are viscous, non-volatile, non-toxic, water-soluble or water-miscible liquids at room temperature. Suitable humectants include, but are not limited to, polyhydric alcohols such as glycerol, sorbitol, ethylene glycol, propylene glycol, polyethylene glycols (PEG) of varying molecular weights including PEG 300, PEG 400 and PEG 600, polypropylene glycols, Their combinations and the like. The humectant can be used in combination with water or without water. When used with water, the ratio of water to the humectant can be from about 1:10 to about 10: 1.

As mentioned above, in use, a hydrogel of the present disclosure may contain the polymer or copolymer and any other additives described herein in an amount from about 20% by weight to about 97% by weight, the remainder being water. and / or a humectant in an amount from about 3% by weight to about 80% by weight of the hydrogel.

An example of an appropriate polymer that can be used as the hydrogel includes RG-63B, commercially available from Covidien.

The monomers and any additional components described above may be mixed and sprayed or coated as a layer on a removable coating, for example a siliconized removable substrate such as a silicone coated polyethylene terephthalate film, or other substrate before polymerization. Free radical polymerization can be initiated by, for example, heating the mixture when a thermal free radical polymerization initiator is present in the mixture, or exposing the mixture to actinic radiation when a polymerization initiator is present in the mixture. free radicals photoinitiated. Any source or 40 convenient sources of actinic radiation that provide wavelengths in the area of the spectrum that overlaps the absorption bands of the photoinitiated free radical polymerization initiator can be used to activate the polymerization. The radiation can be natural or artificial, monochromatic or polychromatic, not coherent or coherent, and for high efficiency it should correspond closely in wavelengths with the absorption bands of the polymerization initiator. Conventional light sources include fluorescent lamps, mercury vapor lamps, additive metal lamps, and arc lamps. Useful lasers are those whose emissions fall into or overlap with the absorption bands of the photoinitiated free radical polymerization initiator. Although, if desired, the mixture can be degassed before polymerization and / or polymerization can be performed in an inert atmosphere, then it is not necessary to degasify the mixture before polymerization or polymerization in an inert atmosphere. fifty

After polymerization the resulting composition can be transferred to a conductive substrate. Alternatively, the conductive composition may be adhered to a conductive substrate, and the removable liner may be left in place to protect the conductive composition until it is ready for use.

Component indicating change

In accordance with the present description, an electrode of the present description also has a component that can be used to indicate that the life of the hydrogel has expired or is about to expire. This indication will identify an end user that the electrode in use should be replaced and that a new electrode should be used. In some embodiments the component indicating that it is time to change the electrode can be included in the

hydrogel described above as part of a conductive composition. In other embodiments, the component indicating that it is time to change the electrode may be an independent component applied to an electrode that is not included in the hydrogel described above.

In the embodiments, a pH indicator can be added to the hydrogel or used independently to indicate that it is time to change or replace the electrode. The pH indicator component may change its color or opacity by being exposed to a pH change, thus providing an indication to replace the electrode. For example, in some embodiments, when the electrode is used, hydrolysis of the hydrogel occurs. Hydrolysis of water in the hydrogel can increase the concentration of hydrogen ions in the hydrogel on the anode side, which reduces the pH of the hydrogel. The hydroxyl ion increases in concentration and on the cathode side the hydrogel pH will increase. The pH indicator can be selected so that it develops a color or opacity, or changes color, when pH 10 decreases or increases depending on whether it is looked at the anode side or the cathode side.

A pH indicator can provide two reasons to indicate the end of the life of an electrode: the loss of water increases the impedance of the electrode, which in turn generates heat, thus changing an electrode in response to the pH indicator heat burns can be avoided; and the decrease in pH indicates the generation of acid due to hydrolysis, or an increase in pH indicates that the production of hydrogel ions, thus changing an electrode in response to the pH indicator, chemical burns can be avoided.

Appropriate pH indicators that may be used include, but are not limited to, bright green, bromophenol blue, m-cresol purple, m-cresol red, eosin Y, methyl orange, methyl violet, combinations thereof and the like. The pH indicator may be present in a hydrogel in a suitable amount from about 50 ppm to about 1,000 ppm, in the embodiments being from about 100 ppm to about 900 ppm.

Suitable pH indicators are commercially available from suppliers such as Aldrich Chemicals, Riedel de Haen, Mallinckrodt Chemicals, Spectrum Chemicals and the like. Details regarding some of the above pH indicators are listed below, as well as others, which can be used in accordance with the present description. 25

The bright green (C27H34N2O4S) supplied has approximately 90% active crystals, and can be used as approximately 1% solution in water. The bright green is yellow at a pH of about 0 to about 2.5 and green at a pH of about 2.6 and higher.

The bromophenol blue (C19H10Br4O5) supplied is an active solution in water approximately 0.04%, and the same in use. Bromophenol blue is yellow at a pH less than about 3, and purple at a pH of about 4.6 and higher.

The purple m-cresol (C21H13O5S) supplied is composed of approximately 90% active crystals, and can be used as a solution in water at approximately 0.04%. Purple m-cresol is yellow at a pH of approximately 1.2 and lower, and purple at a pH of approximately 2.8 and higher.

The red m-cresol (C21H13O5S) that is supplied is a 0.04% active solution in water, and the same in use. Red bromophenol is orange at a pH of about 2 and lower, and yellow at a pH of about 3 and higher.

The eosin Y (C20H8Br4O5) supplied is an active solution in water approximately 5%, and approximately the same in use. Eosin Y is orange at a pH of about 0, and yellow at a pH of about 3 and higher.

The methyl orange (C14H14N3NaO3S) that is supplied is approximately an active solution in water at approximately 5%, and approximately the same in use. Methyl orange is orange at a pH of approximately 3.1 and lower and yellow at a pH of approximately 4.4 and higher.

The methyl violet (C24H28N3Cl) supplied is composed of approximately 75% active crystals, and can be used as a solution in water at approximately 0.02%. Methyl violet is yellow at a pH of about 0 and lower, and violet at a pH of about 1.6 and higher. Four. Five

The phenolphthalein (C20H14O4) supplied is approximately an active solution in 1% alcohol, and the same in use. Phenolphthalein is colorless at a pH below about 8 and fuchsia at a pH greater than about 8.

Bromocresol green can be used at a concentration of approximately 0.1% in water. Bromocresol green is yellow at a pH of approximately 3.8 and lower, and blue at a pH of approximately 5.4 and higher.

The bromocresol-methyl red green is pink at a pH of about 4.6 and lower, and green at a pH of about 5.6 and higher.

Bromocresol purple can be used at a concentration of approximately 0.1% in water. Bromocresol purple is yellow at a pH of approximately 5.3 and lower, and purple at a pH of approximately 6.8 and higher.

Bromothymol blue can be used at a concentration of approximately 1% in water. Bromothymol blue is yellow at a pH of about 6 and lower, and blue at a pH of about 7.6 and higher.

Congo red can be used at a concentration of approximately 1%. Congo red is blue at a pH of approximately 3 and lower, and red at a pH of approximately 5 and higher.

Methyl red can be used at a concentration of approximately 0.1% in water. Methyl red is pink at a pH of approximately 4.2 and below, and yellow at a pH of approximately 6.2 and above.

Phenol red can be used at a concentration of approximately 0.04% in water. Phenol red is yellow at a pH of approximately 6.8 and lower, and red at a pH of approximately 8.2 and higher.

Thymol blue can be used at a concentration of approximately 0.4% in water. Thymol blue is red at a pH of approximately 1.2 and lower, yellow at a pH of approximately 2.8, and blue at a pH of approximately 9.2 and 10 higher.

As mentioned before, in the embodiments combinations of pH indicators can be used.

In some embodiments, a pH indicator can be selected that undergoes a change in its appearance, for example a color change or that develops its color or opacity, at a pH from about 2 to about 4, in embodiments from about 2.25 up to about 3.25. In another 15 embodiments, the dye used can develop a color, a color change or become opaque at a pH from about 8 to about 10 when the electrode is used as described above.

In addition, in the alternative embodiments, after the change of color or opacity a message or symbol could be made indicating that it is time to change or replace the electrode. Any symbol indicating a time to change the electrode could be used. Non-limiting examples of such symbols are: "N", "NG", "S", "Stop", "End", 20 "Replace", a skull and tibia, a disapproving face, a combination of them, and the like .

Medical electrodes

Medical electrodes transmit electrical signals or currents to or from a patient's skin and an external medical device. Medical electrodes are within the scope of those skilled in the art. These electrodes may include a conductive composition such as a hydrogel of the present disclosure on a substrate. Layer 25 of the conductive composition may adhere to, or be in contact with, the patient's skin. The medical electrode may also include a conductive interface that is electrically connected to the layer of the conductive composition and adapted to be electrically connected to an element of an external medical equipment. For many applications the conductive composition should be adhesive enough to adhere to the patient's skin, that is to be a conductive adhesive. The configuration of the electrode and the required adhesive properties will depend on the intended application, such as if the electrode were a transmission electrode, that is, an electrode that sends electrical currents or signals to the patient's body, or a sensing or monitoring electrode. , that is, an electrode that sends electrical signals from the patient's body to the external medical team.

Figure 1 and Figure 2 show a medical electrode 10 on the detachable liner 12. The detachable liner 12 is a removable paper or film of a waxed or coated plastic, such as a silicone coated polyethylene terephthalate film, which can be used to protect the medical electrode 10 before applying the electrode to a skin surface.

The electrode 10 includes a layer of a hydrogel of the present description as conductive composition 14. The electrode 10 also includes the conductive interface 16 having a conductive member with a conductive part 18 that contacts the layer of the conductive composition 14 and with the tongue portion 20 extending beyond the layer of the conductive composition 14 for mechanical and electrical contact with the external medical equipment, such as an electrocardiogram monitoring machine (ECG), an encephalogram machine (EEG), or a transcutaneous electrical nerve stimulation machine (TENS) (not shown). The conductive interface 16 includes the conductive layer 24, coated on at least the side 22 of the conductive interface 16. The conductive layer 26 contacts the layer of the conductive composition 14. The medical electrode 10 can be used as an electrode. diagnostic electrocardiogram (ECG or EKG) or as a transcutaneous electrical nerve stimulation machine (TENS). In use, the removable liner 12, if present, is removed. The layer of the conductive composition 14 of the electrode 10 is applied to the surface of the patient's skin and is connected to the external medical equipment.

Figure 3 shows a straight section of a medical spring electrode 30 in a detachable liner. The electrode 30 has a non-conductive reinforcement 32 having the opening 33 covered by the spring 34 through which 50 the buttonhole 35 protrudes. The spring 34 is fixed to the buttonhole 35. The spring 34 and the buttonhole 35 together provide at least part of a conductive interface adapted to provide an electrical connection between a flexible conductive layer 36 and the external medical equipment (not shown). The eyelet 35 and the reinforcement 32 are covered by the flexible conductive layer 36 which, in the embodiments, can be made of a material such as carbon vinyl. A hydrogel of the present description can be used as a conductive composition 40 and adhered to the conductive layer 36. The removable liner 55 protects the conductive composition 40 before use. In embodiments, a total or partial layer of

Silver and / or a silver salt such as silver chloride can be placed between the conductive composition 40 and the conductive layer 36 (not shown), applied as a coating on at least a portion of a surface of the conductive layer 124. In embodiments, the electrode may include silver (Ag) or silver / silver chloride (Ag / ClAg) disposed on at least a portion of the first and / or second sides of the conductive layer.

As mentioned before, in the embodiments an electrode may have a message or symbol that becomes visible or darkens after use indicating that it is time to be replaced. Such a message or symbol, In embodiments, can be placed on the surface of the conductive layer 36 adjacent to the hydrogel 40 (not shown).

In addition, in the embodiments, the conductive layer 36 and the non-conductive layer 32 may have adjacent windows of each other in each layer (not shown) that allow the visualization of the conductive composition 40 during use, so that the color change, opacity, and the like with an electrode placed in a patient. 10

In other embodiments, as described above, a heat sensitive component such as a wax or a thermochromic material may be applied on a buttonhole 35 (not shown) or a portion of a buttonhole 35 (not shown) adjacent to the non-conductive reinforcement 32. The heat sensitive component may melt, become clear, or change color after repeated use and provide an indication of when an electrode should be changed.

Figure 4 shows a straight section of an alternative medical electrode 100 on a removable coating 112, 15 which may be a polyester film or any other material suitable for use as a removable coating. The electrode 100 includes a layer of a hydrogel of the present disclosure that has a pH indicator as described above as conductive composition 114. In embodiments, the conductive composition 114 may have a reinforcing member 113 embedded in the hydrogel, the which can be a woven or non-woven mesh or any other material such as a diffuser gauze, suitable for forming a reinforcing member. The electrode 100 20 may also have a conductive layer 124 which may be in suitable embodiments a suitable material such as a conductive carbon film of a suitable thickness, in embodiments of approximately 2 mils. In some embodiments a flow coating or a partial coating of silver ink 115 (which may be silver and / or silver chloride) may be between the conductive layer 124 and the conductive composition 114, applied as a coating on at least one part of a surface of conductive layer 124. In embodiments, electrode 25 may include silver (Ag) or silver / silver chloride (Ag / ClAg) disposed on at least a portion of the first and second sides of the conductive layer.

The electrode 100 may also have an electrical conductive wire of the pig tail type 160 of stainless steel or tin / copper with an appropriate length. In embodiments from about 5 to about 15 inches long, in other embodiments being approximately 9 inches in length. The electrical conductor 160 30 may have an insulating cover which, in turn, may be attached to a conductive layer 124 using an adhesive 170. The electrode 100 may also have a reinforcing film 150 having a sensitive medical grade adhesive thereon. at the pressure (PSA) covering the electrical conductor 160 and fixing the reinforcing film 150 to the conductive layer 124 and the covering material 180. Finally, the covering material 180 may have a pull tab 190 notched out of the covering material 180 at the end of the electrode 100 opposite the end at 35 whose interior the electrical conductor 160 is inserted into the electrode.

Medical electrodes may be packaged for use in any suitable materials within the scope of those skilled in the art. For example, the electrodes may be packaged in materials such as polyethylene or other plastic films, laminar screen packaging, combinations thereof, and the like.

Industrial Applicability 40

The conductive compositions of the present disclosure may be useful with medical electrodes that can be used with medical equipment for a variety of applications such as: electrocardiogram monitoring electrodes (ECG) (tongue and spring type) for monitoring cardiac activity and for the diagnosis of cardiac abnormalities; electroencephalogram electrodes (EEG); Transcutaneous electrical nerve stimulation electrodes (TENS) used for pain management; neuromuscular stimulation (NMS) used to treat 45 conditions such as scoliosis; muscle stimulation electrodes; wound treatment electrodes (accelerated healing of skin wounds or broken bones); defibrillation electrodes to supply electrical energy to a chest cavity of a mammalian patient to defibrillate the patient's heartbeat; ionophoresis; and dispersive electrodes to receive the electrical energy supplied inside an incision made during electrosurgery. Other applications of the conductive compositions of the invention include, for example, electrosurgical dispersive pads 50; medication supply (passive or ionophoretic); pre-surgical limbo or area markers, ribbons (chest anchor tubes, NG tubes, IVs cannulas, etc); and sterile seals at points of entry of needles or cannulas. The medical equipment used in these applications is within the reach of those skilled in the art.

EXAMPLE 1

A hydrogel sample containing phenolphthalein was prepared as a pH indicator. The object was to see if a change in the pH of the hydrogel due to hydrolysis was significant enough to be observed throughout its use. Approximately 49.5 grams of RG-63B monomer solution (lot # 07686, manufactured on 09/25/07) was combined with approximately 0.5 grams of a 1% phenolphthalein solution in alcohol.

The monomer solution was first weighed in a 200 ml clean glass beaker. Phenolphthalein solution was added thereto and the mixture was placed in an electric mixer with a blade-type propeller and mixed for approximately 5 minutes bringing the vortex down halfway the mixing shaft. The mixture stopped and the shaft was cleaned. A 25-millimeter thick sheet of the monomer was formed on a non-woven polyester diffuser gauze on a removable 5 mil polyester coating. The film was irradiated for approximately 30 seconds under an Xenon arc UV lamp. The resulting polymer film was covered with a detachable 2.5 mil ethylene liner, bagged and sealed in a polyester foil bag. TENS electrodes were made that include this hydrogel. The hydrogel sides of the electrodes were placed in a conductive gel that simulated the skin and tissue. They were attached to a commercial TENS device and electrical stimulation began. After approximately four hours of stimulation the hydrogel on the side of the cathode turned to fuchsia, indicating that the pH of the hydrogel was 8 or higher.

It will be appreciated that several of the aforementioned features and functions and others, or alternatives thereof, can be conveniently combined in many other different systems or applications. It will also be appreciated that the various alternatives, modifications, variations and improvements therein currently unforeseen or unanticipated can be made by those skilled in the art, which are also intended to be contained in the following claims. Unless specifically stated in a claim, the steps or components of the claims should not be contained in or removed from the specification or any other claims as to any particular order, number, position, size, or material.

In one embodiment, the hydrogel comprises a component selected from the group of gelatin, polysaccharides, crosslinked acrylamide polymers, polymerized hydroethyl methacrylate polymers, polymerized crosslinked polyhydroacrylate, 20 polymers of crosslinked 2-acrylamide-2-methylpropane sulfonic acid, polycyclycrylic acid, crosslinked polyvinyl acrylamide copolymers of the foregoing, one or more salts thereof, and combinations thereof, and wherein the hydrogel optionally further comprises an electrolyte present in an amount from about 0.5% by weight to about 10% by weight of the hydrogel and optionally further comprises a neutralizer selected from the group consisting of ammonium hydroxide, sodium hydroxide, potassium hydroxide, lithium hydroxide and combinations thereof.

In another embodiment the hydrogel comprises a copolymer having a first monomer having a mixture of acrylic acid and a salt thereof present in an amount from about 8% by weight to about 85% by weight of the hydrogel, and a second monomer of formula CH2 = CHC (O) XR, wherein X is O or NH and R is an unsubstituted or substituted alkyl group from about 1 to about 5 carbon atoms present in an amount from about 15% by weight to approximately 92% by weight of the hydrogel.

Preferably, the hydrogel further comprises a crosslinked agent selected from the N-N'-methylene bis-acrylamide group, diethylene glycol diacrylate, diethylene glycol dimethacrylate, trimethylpropane triacrylate, trimethylpropane trimethacrylate trimethylpropathylated trimethylpropathylate trimethylpropathylate , pentaerythrol triacrylate, pentaerythritol trimethacrylate, pentaerythritol tetracrylate, pentaerythritol tetramethacrylate, 35 polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, and combinations thereof, optionally a polymerization initiator from the group of 1-butyl group from the group of bisbutyl to the group of 1-butyl group -hydroxycyclohexyphenyl, 2-hydroxy-2-methyl-1-phenylopropane-1-one, 2-hydroxy-1- [4- (2-hydroxyethoxy) phenyl] -2-methyl-1-propane-1-one, 22, 2-dimethoxy-2-phenylacetophenone, benzophenone, and combinations thereof, and in which the electrode further comprises a conductive layer has a coating of silver or silver / c Silver loride in at least a part of a surface of the conductive layer. 40

Advantageously, at least one pH indicator is selected from the group of bright green, bromophenol blue, m-cresol purple, m-cresol red, eosin Y, methyl orange, methyl violet, phenolphthalein, bromocresol green, bromocresol blue, bromothymol blue, red Congo, methyl red, phenol red, thymol blue, and combinations thereof, present in the hydrogel in an amount from about 50 ppm to about 1,000 ppm.

Preferably, the indication for replacing the electrode comprises a symbol or message. Four. Five

Claims (9)

1. A medical electrode comprising: a substrate; Y a conductive composition (14, 40, 114) in at least a part of a surface of the substrate, in which the conductive composition comprises at least one hydrogel and characterized in that the conductive composition 5 further comprises at least one pH indicator component that will change its color or opacity from exposure to a change in pH, which provides an indication to replace the electrode. 2. The medical electrode of claim 1 wherein the hydrogel comprises a component selected from the gelatin group, polysaccharides, cross-linked acrylamide polymers, cross-linked hydroxyethyl methacrylate polymers, 2-acrylamide-2- sulfonic acid polymers crosslinked methylpropane, crosslinked polyvinylpyrrolone 10, polyacrylic acid, copolymers of the foregoing, one or more salts thereof, and combinations thereof, and in which the hydrogel optionally further comprises an electrolyte present in an amount from about 0.5% in weight up to about 10% by weight of the hydrogel, and optionally further comprises a neutralizer selected from the group of ammonium hydroxide, sodium hydroxide, potassium hydroxide, lithium hydroxide, and combinations thereof. fifteen 3. The medical electrode of claim 1 wherein the hydrogel comprises a copolymer having a first monomer comprising a mixture of acrylic acid and its salt present in an amount from about 8% by weight to about 85% in weight of the hydrogel, and a second monomer of formula CH2 = CHC (O) XR, wherein X is O or NH and R is an unsubstituted or substituted alkyl group from about 1 to 5 carbon atoms present in an amount of about 15% by weight to about 92% by weight of the hydrogel. 4. The medical electrode of claim 1 wherein the hydrogel further comprises a crosslinking agent selected from the group of N-N'methylene bisacrylamide, diethylene glycol diacrylate, diethylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, triacrylate of ethoxylated methylolpropane, ethoxylated trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, pentaerythritol tetracrylate, pentaerythritol tetramethyl acrylate, polyethylene glycol, polyethylene group, 2-polyethylene glycol group 2-azobisisobutyronitrile, 1-hydroxy-cyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, 2-hydroxy-1 [4- (2-hydroxyethoxyphenyl] -2-methyl-1-propane-1- one, 2,2-dimethoxy-2-phenylacetophenone, benzophenone, and combinations thereof, and wherein the electrode further comprises a conductive layer qu e has a silver or silver / silver chloride coating on at least a part of a surface of the conductive layer. 5. The medical electrode of claim 1 wherein at least one pH indicator is selected from the group consisting of bright green, bromophenol blue, m-cresol purple, m-cresol red, eosin Y, methyl orange, methyl violet, Phenolphthalein, bromocresol green, bromocresol purple, bromothymol blue, Congo red, methyl red, phenol red, bromothymol blue, and combinations thereof. 35 6. The medical electrode of claim 1 wherein at least one pH indicator undergoes a change in appearance at a pH from about 2 to about 4. 7. The medical electrode of claim 1 wherein at least one pH indicator undergoes a change in appearance at a pH from about 8 to about 10. 8. The medical electrode of claim 1 wherein at least one pH indicator is present in the hydrogel in an amount from about 50 ppm to about 1,000 ppm, and wherein the electrode replacement indicator comprises a symbol or message.